This invention relates generally to an electrical apparatus adapted for use as a diagnostic aid in determining certain physical conditions of a patient, and more particularly, the present invention relates to an electrical apparatus which is designed to measure the reflex action of the Achilles tendon as an aid in the diagnosis of thyroid malfunctions and the treatment of those malfunctions.
The original concept for measuring the reflex duration of the Achilles tendon after it has been tapped by a reflex hammer consisted of a platform on which the patient's foot rested. Measurements of the reflex duration were made by observing the pressure changes on the platform under the foot. This pressure change could then be translated into a chart to form a permanent record for subsequent study and comparison. Certain subsequent systems utilized an apparatus which simplified the measuring of the reflex action and particularly utilized a strain-gauge transducer and an electro-optical system.
The concept of utilizing the reflex action of the Achilles tendon as an aid in the diagnosis of thyroid malfunctions and the like has been known in the past.
Certain prior art systems, for example, utilized a permanent magnet which is attached to the heel of the patient by use of adhesive tape. A measuring head, having a fixed electrical coil, is positioned a few inches from the magnet on the heel. The electrical coil in then connected to a standard ECG unit so as to produce a visual trace on a standard ECG chart. Thus, when the Achilles tendon is tapped with a reflex hammer, the movement of the magnet with respect to the coil will produce an impulse whose shape will determine the visual trace on the ECG chart.
Another prior proposed system involved the use of a noncontacting capacitor wherein the patient's foot is placed between the plates of the capacitor. The Achilles tendon is tapped with a percussion hammer and the reflex action is sensed by a change in capacitance of the capacitor. This change is applied to a detector system and a read-out is provided for the operator.
Finally, a system was introduced which utilized a photoelectric device, commonly referred to as the photomotograph, used in conjunction with a standard direct-writing electrocardiograph to permit a simple recording of foot movement. A tap on the Achilles tendon with a percussion hammer causes the patient's foot to move in the light beam, generating a change in photocell voltage which is then recorded on the electrocardiograph paper to give a time position plot of reflex action.
While these prior art systems have proved satisfactory, it has been found desirable to improve the systems for measuring the tendon reflex. With the system of the present invention, a simple office procedure is performed with ease and with a minimum expenditure of time by the physician. The procedure can be performed by the physician's assistant in a matter of a few moments and the results evaluated while the patient is still in the office. Thus, it is ideally suited for an out-patient type of operation in a physician's office. Further, it can be used as a test for screening thyroid patients and following their progress under medication.
Further, the test, as performed by the system of the present invention, could become a valuable part of the complete physical examination record which may be utilized for future comparison as is now commonly recommended for electrocardiograms. With this test, the physician can easily follow the patient's response to therapy, regardless of the type of therapy utilized.
Further, it has been suggested, for example, that one in every twenty persons in the United States have a malfunctioning thyroid glad and this condition causes the patient to carry a higher risk of heart attack, some cancers, and a sluggish functioning of the brain. For this reason, it has been suggested to institute mass screening tests to detect this condition in order that these people may receive the proper medical attention. The simplicity in performing the Achilles reflex test and its accuracy in screening hypothyroid patients particularly lends itself to such mass testing procedures.
With the system of the present invention, an input transducer is interconnected with the patient to provide an output signal indicative of the displacement of the foot in response to the tapping of the Achilles tendon with a percussion hammer. This transducer may take various forms, and for example, the photoelectric technique described above wherein a lamp and a condensing lens in one side of a U-shaped housing directs a beam of light on a photovoltaic cell on the other side of the U-shaped housing. The patient is then positioned in a kneeling configuration on a chair or specially designed kneeling bench. The unit is positioned so that the light beam is partially intercepted by the metatarsal region of the foot. Upon tapping the Achilles tendon with the percussion hammer, the patient's foot is caused to move in the light beam to generate the change in voltage from the photoelectric cell described above.
The output from the transducer is set to an input amplifier which amplifies the signal from the transducer. The output of the input amplifier is fed in one instance to a peak detector and holder circuit which is utilized to detect and hold the highest peak sensed before the peak holder is reset. The output of the peak holder is fed through a one-half voltage divider and then to the input circuit of a comparator circuit. The output of the input amplifier is also fed directly to the input of the comparator circuit wherein the two signals are compared to detect a cross-over when the output of the one-half peak voltage divider exceeds the output from the input amplifier. When this condition occurs, an output signal is generated by the comparator circuit.
This output signal from the comparator circuit is fed to a flip flop which is triggered to the opposite state with every positive going pulse edge from the comparator circuit. As will be seen from a further description of the drawings, positive going edges occur when the reflex wave form reaches one-half of its amplitude in the initial peak and subsequently reaches one-half of its amplitude in a subsequent peak. The output of the flip flop is fed to an integrator circuit which provides a time reading of the duration of the period during which the flip flop was triggered to its opposite state. This output is then fed to a meter or to some other type of output indicating device.
The system further includes an input offset compensator which is a circuit connected to the input amplifier for providing a compensating voltage for the input amplifier to force the input amplifier to provide a zero output signal when there is zero input from the transducer. The system further includes a reset switch which is connected to the input offset compensator circuit, the peak holder circuit, the flip flop circuit, and the integrator circuit to reset and initialize these circuits prior to taking a measurement.